How many days does it take for concrete strength to grow?

Depending on the temperature, the number of days required will vary, and the specific schedule is as follows.

The concrete grade is represented by the 90-day age period, and now the engineering quality inspection is based on the measured compressive strength value of 28 days, because 28 days can already reflect the strength of concrete. The concrete elements are tested for 7-day compressive strength, and if 75% of the design strength is reached, the formwork is allowed to be removed.

Concrete should reach 30% of the design strength in 3 days.

In general, ordinary concrete, three days up to more than 30%. 50% for 7 days and 70% for 14 days. The increase in the strength of the actual poured concrete is related to many factors.

For example, the fineness of cement, the cement is fine, the hydration reaction is fast, the early strength is high, and it reaches 50% or more in three days in summer. There are also maintenance conditions, the temperature is higher, the coverage is better, and the maintenance is timely and the intensity is improved quickly.

Concrete strength.

Common causes of insufficiency.

1. Poor quality of raw materials.

Concrete is made of cement, sand, stone, water, and admixtures mixed in a certain proportion, and the quality of raw materials directly affects the strength of concrete.

2. Failure to construct in accordance with the mix ratio and incorrect construction technology.

1) Excessive water consumption.

The more common ones are the inaccuracy of the water filling device on the mixer; The moisture content of sand and gravel is not deducted.

Even in order to facilitate the construction, water is arbitrarily added to the pouring site. In addition to the strict measurement of water, the prevention and control of this phenomenon should also be based on the moisture content of sand and gravel at the time.

It is incorrect to convert the laboratory mix ratio to the construction mix ratio, and the construction according to the laboratory mix ratio is incorrect.

2) The dosage of admixtures is inaccurate.

Ordinary type superplasticizer.

Such as lignin. Excessive dosage of calcium sulfonate, calcium sugar and other amounts is the most common inaccurate dosage. When the overmixing is serious, it will cause a permanent shortage of concrete strength, and it is worth noting that the low amount of dosage will also make the 28d strength not meet the requirements, but the strength of the long age can still reach the strength of blank concrete.

3 days later. The newly paved cement floor generally begins to "initial setting" in 4-6 hours (in summer, longer in winter), and reaches about 70% of the maximum strength in about three days, and reaches the highest strength of cement design in 28 days. Under normal circumstances, if the ground of the new section is closed to traffic for the time being, it should be able to be paved after 48 hours, and it should be allowed to be opened to traffic until it is completely solidified.

Winter concrete construction methodIt is necessary to reasonably reduce the water-cement ratio, and according to the actual situation of the construction project, reasonably reduce the water-cement ratio, and reasonably increase the amount of cement, so as to increase the heat of hydration, so as to shorten the time to reach the age intensity.

Doped with air-entraining agent. In order to improve the fluidity of the mixture, thereby improving its cohesion and water retention, buffering the water pressure caused by the freezing of water in the concrete, and improving the frost resistance of the concrete, the bubbles generated after the air-entraining agent can be added to increase the volume of the cement slurry accordingly.

It takes 28 days for coagulation to reach strength.

The hardening of concrete is divided into two stages, one is the solidification stage, and the other is the strength growth stage. Coagulation phase. The final setting of concrete is generally about 8 hours after pouring, and the concrete begins to increase in strength after final setting.

Intensity growth phase. The design strength can be reached 28 days after pouring. The concrete strength test and evaluation is based on this.

But the growth of concrete strength is not over, but is still growing slowly. Half a year or even a year later, the intensity has grown. Hardened concrete is called hardened concrete, and the properties of hardened concrete mainly include strength, deformation and durability.

Concrete pouring

It refers to the process of pouring concrete into the mold until plasticization, and in civil engineering and construction projects, concrete and other materials are made into a predetermined shape into the mold, and when the concrete is poured, the free height of the concrete should not exceed 2m, and corresponding measures should be taken when exceeding the excitation oak 3m.

The formwork rights, steel bars, parts and pipelines of the poured concrete layer have all been installed, and the design requirements have been checked to meet the design requirements, and the hidden and pre-inspection procedures have been completed. The concrete scaffolding and horse road have been erected and have been inspected. Cement, sand, stone and admixtures have been inspected to meet the requirements of relevant standards, and the laboratory has issued a notice of concrete mix ratio.

The scale (or automatic feeding system) is checked and verified to be accurate in measurement, and the vibrator (rod) is qualified after inspection and trial operation. According to the construction plan, the foreman has carried out comprehensive construction technical training for the operation team, and the concrete pouring application has been approved.

Summary. 4. Durability: Concrete itself is a material with good durability.

Dear, hello teacher is very happy to answer for you, I found that the concrete can generally reach strength after 28 days, during this period one is the solidification period, the other is the growth period, the setting time is within 8 hours after pouring, the strength growth period will not reach the expected strength until 28 days after pouring, and in the next 6 months will slowly grow in the beam starvation zone. The advantages of concrete are:

1. Plasticity: Modern concrete can have a very careful workability, and can almost arbitrarily form buildings and components with different forms by setting cracks and formwork, with strong plasticity;

2. Economical: Compared with other materials, concrete is low, easy to use local materials, and the maintenance cost after the structure is completed is also low;

3. Safety: Hardened concrete has high mechanical strength and strong adhesion with steel bars, so that the structural safety is guaranteed;

4. Durability: Concrete itself is a material with good durability.

Give you a reference kiss.

I hope mine can help you.

Generally, the strength of three days is 60% of the design value, 80% for seven days, and 120% for 28 days, and the growth rate is the fastest in the previous day, and the hydration heat of cement is the largest, and it slowly slows down after seven days, and the strength growth also slows down.

The fine aggregate of the prepared concrete is required to be clean and free of impurities to ensure the quality of the concrete. The sand often contains some harmful impurities, such as mica, clay, silt, silt, etc., which adhere to the surface of the sand, hinder the bonding of cement and sand, and reduce the strength of concrete; At the same time, it also increases the amount of water used in the concrete, thereby increasing the shrinkage of the concrete and reducing the frost resistance and impermeability.

Some organic impurities, sulfides and sulfates, which have a corrosive effect on cement. The sand used in important engineering concrete should be tested for alkali activity, and when it is judged to be potentially harmful after inspection, cement with less alkali content should be used when preparing concrete, or admixtures that can inhibit the reaction of alkali and aggregate should be used.

Cement:

Varieties of selection and preparation of concrete can generally use Portland cement, ordinary Portland cement, slag Portland cement, porosyl Portland cement and fly ash Portland cement. If necessary, fast-hardening Portland cement or other cement can also be used. The performance indicators of cement must comply with the provisions of the current national standards.

If it is necessary to use high-grade cement to prepare low-strength grade concrete, the amount of cement will be small, which will affect the workability and compactness, so a certain amount of mixed materials should be mixed. If it is necessary to use low-grade cement to prepare high-strength grade concrete, the amount of cement will be too much, uneconomical, and it will affect other technical properties of concrete.

In the environment of room temperature and humidity, the strength of concrete is a continuous development process, but the strength development rate is high in the early stage (14 days ago), and the strength growth rate in the later stage gradually decreases. This is determined by factors such as the mineral composition of the cement, the composition of the cementitious material, the amount of water added, and the ambient humidity. In a laboratory environment, tests have shown that after 10 years, there is a slight increase in concrete strength.

Therefore, it is normal to have a large increase in intensity after 28 days.

The general rule: the use of pure silicate, fast-hardening cement, mixed with silica fume or ultra-fine mineral powder, the early strength of concrete development block, the later strength growth potential is small. The use of mineral admixtures such as fly ash and mineral powder will have a slower strength development in the early stage, but there will be a greater strength increase in the later stage, because the hydration process of fly ash and ordinary fineness mineral powder is slower.

Therefore, some projects set the standard strength test age of fly ash concrete as 56 days, and even set the test age as 90 days for large amount of fly ash concrete. The aim is to make the most of the actual strength of the fly ash concrete, as the structure is not put into use after 28 days, and it often takes three months or more for the load to actually bear the load.

In addition, the strength of concrete may also shrink, which is mostly seen in actual concrete structures. For example, internal destruction such as alkali-aggregate reactions, delayed aluminite formation, etc., has occurred. For example, due to the action of damaging factors in the environment, high-temperature dehydration (above 100 degrees), freeze-thaw, chemical corrosion, sulfate erosion, and so on.

The increase in the strength of concrete is due to the progress of cement hydration, and when the hydration is basically completed, the strength of concrete will not increase significantly.

The later stage is mainly C3S

C2S works.

Generally speaking, 28 days is the standard time for experimental testing, but it does not mean that after 28 days, there will be no major change in the strength of concrete. Due to the influence of cement varieties, water-cement ratios and so on, a lot of concrete 28

There is still a more obvious increase in intensity after the day.

This is not very clear, generally the three-day intensity is 60% of the design value, 80% for seven days, 120% for twenty-eight days, and the fastest growth rate in the previous day. The heat of hydration of cement is the largest, and after seven days it slowly slows down, and the strength growth also slows down. Three days to seven o'clock to increase about 5-10 map Seven days to 28 days to increase 12-18, in short, the material is different, the environment is different, the growth is not the same.

Hello! Concrete strength increases greatly within 28 days of preparation. In general, the strength of concrete will increase by 20% to 50%.

And the concrete strength will have a large increase every balance fiber day, about 30 in the 1 7-day period, about 15% in the 7-28 day period, mostly 30; The specific situation of Tikai will also be affected by factors such as concrete composition and construction technology.